This Part Fits the following kits / parts:

#88073 - DIFFERENTIAL LOCKER (SPOOL DIFF HUB/2pcs)

For 87633 WHEELY KING ROCK CRAWLER CONVERSION SET

Genuine HPI quality spare part for #87633 Wheely King Rock Crawler Conversion
Set, allowing easy maintenance and repairs. Anyone looking to
customize their Wheely King to solid axles should have a set of
these! You get a pair of diff lockers that provide you with a solid
axle and add extra weight where it's need: down low.